Bluelab pH Pen | Waterproof pH & Temperature Meter, 0.0-14.0 pH

What the Bluelab pH Pen Reads and How Accurately

A pH reading that drifts is worse than no reading, because you feed on it. This pen covers 0.0 to 14.0 pH at 0.1 resolution and holds ±0.1 pH accuracy at 25°C. A double junction probe does the work. It also reads solution temperature across 0-50°C / 32-122°F and compensates automatically, so a cold reservoir at lights-on does not throw the number. The body is fully waterproof and the LCD is backlit for a dark room. A hold function freezes the reading so you can pull the probe out before squinting at it. One AAA battery, with a low-battery warning before it strands you mid-feed.

Calibration and Probe Care on a Hydroponic pH Meter

Calibrate against fresh 4.0 and 7.0 solution and keep the tip in storage solution between uses, never dry and never in plain water. A dried-out junction is what kills these pens, not the electronics. The pen tells you when a calibration takes, which is the difference between trusting a number and hoping. Here is the honest limit: the double junction probe is not replaceable, so when it finally goes, the pen goes with it. If you want a probe you can swap, step up to a Bluelab meter with a BNC connection. Also worth saying plainly, this reads solution, not root zone. Growers testing soil directly want the Bluelab Soil pH Pen instead.

Key Features

• 0.0 to 14.0 pH at 0.1 resolution: Plus or minus 0.1 pH accuracy at 25C, tight enough to feed on.
• Automatic temperature compensation: Corrects the reading against solution temperature from 0-50C, so a cold reservoir does not skew the number.
• Fully waterproof body: Survives being dropped in the tank, which is where most pens end their careers.
• Backlit LCD with hold function: Freezes the reading so you can lift the probe and read it in a dark flower room.
• Successful calibration indicator: Confirms the calibration took instead of leaving you guessing whether the pen is telling the truth.

Technical Specifications